Fatty acid monoglycerides used widely as an oil agent and the like in cosmetics, foods, and industrial emulsifiers or lubricants are produced by esterification reaction of glycerin with fatty acid or by ester exchange reaction of glycerin with fat and oil.
Those reactions are carried out in the absence or presence of a catalyst, and generally a mixture of glycerin, fatty acid monoglyceride, fatty acid diglyceride, and fatty acid triglyceride is generated.
For such reasons, a purification step is required depending on a purpose. When it is desired to obtain a fatty acid monoglyceride with high purity, purification based on molecular distillation or thin layer distillation is performed. Fatty acid diglyceride and fatty acid triglyceride contained in residuals after distillation of monoglyceride can be recovered again as monoglyceride according to a transesterification reaction with glycerin. However, from the viewpoint of production efficiency of monoglyceride, higher purity of the monoglyceride before distillation step is preferred.
As disclosed in JP-A 57-24327, it is known that the equilibrium of the ester exchange reaction shifts to the fatty acid monoglyceride production side as the reaction temperature increases. By maintaining fat and glycerin as a raw material at high temperature like 220° C. or higher in the presence of a catalyst, concentration of the fatty acid monoglyceride increases.
However, when time is required for cooling in the presence of a catalyst, it is known that the reaction toward the equilibrium at that temperature, that is, the reaction from two molecules of fatty acid monoglyceride to fatty acid diglyceride and glycerin, becomes larger, so that the concentration of fatty acid monoglyceride is decreased.
It is then disclosed in JP-A 57-24327 to neutralizing an alkali catalyst with an acid, after completion of the reaction, to inactivate it, decrease the reaction rate and prevent the concentration of fatty acid monoglyceride from decreasing.
It is disclosed in U.S. Pat. No. 2,909,540 to prevent the concentration of fatty acid monoglyceride from decreasing by lowering the reaction rate by evaporating glycerin at a reduced pressure, after the reaction for producing fatty acid monoglyceride, and cooling the liquid of the completed reaction with heat transfer accompanied with evaporation.
In U.S. Pat. No. 3,083,216, production of higher fatty acid monoglyceride is disclosed. In U.S. Pat. No. 3,079,412, continuous production of fatty acid monoglyceride is disclosed.